Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Caltech Researchers Find Evidence of a Planet Beyond Pluto

caltech.edu

Post reply on HN
Print view View original

11–20 of 159 posts

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#11

Post by hmahncke »

antognini wrote: post #9
beamatronic wrote: post #2

Why wouldn't their calculations be able to suggest possible locations for the planet?

They do, and at the end of the press release it says that Brown has begun an observing campaign to find the planet. Unfortunately detecting these very distant objects is very difficult. The light we see from them is reflected light from the Sun, so their apparent brightness goes as 1/r^4, not 1/r^2 like most objects. And because they are so close, there is a strong parallax from the motion of the Earth. THe consequen…

Also, we don't know where in its orbit the planet happens to be right now. If we're lucky, it's relatively close to the sun, and it will be detectable. If we're unlucky, it's relatively far away from the sun, and it could easily be undetectable by current observatories because the orbit is so eccentric.

[Source: I saw Mike Brown give a talk on this topic at the Cal Academy of Sciences, where he hoped he was lucky...]

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#12

Post by nkoren »

If it holds up, this is fantastic. Given how interesting the Pluto system has turned out to be, I can only fantasise about a potential super-earth system relatively nearby.

However, to be completely pedantic: would this actually be a planet? Or still a dwarf planet, despite its massive size? Keep in mind that the definition of planethood is not only that it's large enough to be rounded by its own gravity, but that it has also "cleared its orbit". I get the impression that this would cut through broad swathes of the still-cluttered Kuiper belt, and thus would only qualify as a "dwarf" despite its massive size.

I checked the original papers for references to whether it had cleared its orbit, and couldn't find any. Correct me if I'm wrong?

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#13

Post by daveguy »

antognini wrote: post #9
beamatronic wrote: post #2

Why wouldn't their calculations be able to suggest possible locations for the planet?

They do, and at the end of the press release it says that Brown has begun an observing campaign to find the planet. Unfortunately detecting these very distant objects is very difficult. The light we see from them is reflected light from the Sun, so their apparent brightness goes as 1/r^4, not 1/r^2 like most objects. And because they are so close, there is a strong parallax from the motion of the Earth. THe consequen…

I would expect a smear with characteristics of the planet would be as effective to identify it as a single snapshot. Wouldn't the direction be well identified from indirect detection? Is the blur also less effective because of increased background exposure?

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#15

Post by logingone »

I don't seem to have a grasp of our visibility of our solar system. We can see a number of the planets with the naked eye, a number of the moons with binoculars and a few hundred $/£/€/.. telescope. Yet even with these great big radio telescopes, antenna arrays, Hubble, etc, we seem to be quite unaware of what's in our neighbourhood. Anyone have figures of how much we've surveyed?

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#16

Post by ChuckMcM »

Ah Planet X which is now planet IX with Pluto's demotion :-). I am guessing that you can confirm it by looking for star occulusions. Presumably the planet would blank out stars as it passed between earth and those stars. So would it be possible to find it using existing plates?

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#19

Post by pavel_lishin »

danieldrehmer wrote: post #17

I'm puzzled by how a planet this big could form in an orbit so distant. The fact that the material in that region is so spread out and the orbital period of such object is so long matters. I would love to read some thoughts on that.

It could have formed closer to the sun in the early stages of our solar system, and been flung out into a more irregular orbit after that.

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#20

Post by Symmetry »

nkoren wrote: post #12

If it holds up, this is fantastic. Given how interesting the Pluto system has turned out to be, I can only fantasise about a potential super-earth system relatively nearby. However, to be completely pedantic: would this actually be a planet ? Or still a dwarf planet , despite its massive size? Keep in mind that the definition of planethood is not only that it's large enough to be rounded by its own gravity, but that…

The criteria for clearing an orbit are apparently somewhat involved[1]. It can't just be a matter of no other bodies having the same distance from the sun or Pluto would disqualify Neptune and Jupiter would be disqualified by its trojans. Because the planets in these cases mass so much more than other other nearby bodies those other bodies dance to the planet's tune and aren't counted against the planet in terms of clearing it's neighborhood. But if you look at the large bodies in the asteroid belt or the TNOs then their influence is very much mutual.

It's not entirely obvious if the new body would be a planet under the listed criteria since I don't think we have a good handle on the total trans-Neptunian population. In fact by Soter's µ criteria we might just need a single Pluto-sized object to cross this planet's path to disqualify it.

[1]https://en.wikipedia.org/wiki/Clearing_the_neighbourhood

Post reply on HN